Devices based on GaN and related III-N materials are increasingly well established in RF power applications, and are under active research and development for power conversion and control applications. However, the unique material properties of the III-Ns make them a promising basis for applications well beyond these traditional applications. Novel device concepts that harness these material properties in conjunction with unconventional operational physics are being explored to serve needs in applications as diverse as millimeter-wave and THz electronics and sensing, low-power systems, and ultra-scaled low-power logic. Devices exploiting interband tunneling in III-N heterostructures for low-power logic, as well as impact ionization and plasma-wave propagation in GaN 2DEGs for millimeter-wave and THz sensing and electronics are under active investigation to provide new levels of performance.